The tubular network of the Golgi apparatus |
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Authors: | H H Mollenhauer D James Morré |
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Institution: | (1) Food Animal Protection Research Laboratory, Department of Agriculture, USDA, F&B Road, College Station, Texas 77845-2881, USA, US;(2) Department of Medicinal Chemistry and Pharmacognosy, Purdue University, West Lafayette, Indiana, 47907, USA, IN |
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Abstract: | Golgi apparatus of both plant and animal cells are characterized by an extensive system of approximately 30 nm diameter peripheral
tubules. The total surface area of the tubules and associated fenestrae is thought to be approximately equivalent to that
of the flattened portions of cisternae. The tubules may extend for considerable distances from the stacks. The tubules are
continuous with the peripheral edges of the stacked cisternae, but the way they interconnect differs across the stack. In
plant cells, for example, tubules associated with the near-cis and mid cisternae often begin to anastomose close to the peripheral edges of the stacked cisternae, whereas the tubules of
the trans cisternae are less likely to anastomose and are more likely to be directly continuous with the peripheral edges of the stacked
cisternae. Additionally, the tubules may blend gradually into fenestrae that surround some of the stack cisternae. Because
of the large surface area occupied by tubules and fenestrae, it is reasonable to suppose that these components of the Golgi
apparatus play a significant role in Golgi apparatus function. Tubules clearly interconnect closely adjacent stacks of the
Golgi apparatus and may represent a communication channel to synchronize stack function within the cell. A feasible hypothesis
is that tubules may be a potentially static component of the Golgi apparatus in contrast to the stacked cisternal plates which
may turn over continuously. The coated buds associated with tubules may represent the means whereby adjacent Golgi apparatus
stacks exchange carbohydrate-processing enzymes or where resident Golgi apparatus proteins are introduced into and out of
the stack during membrane flow differentiation. The limited gradation of tubules from cis to medial to trans offers additional possibilities for functional specialization of Golgi apparatus in keeping with the hypothesis that tubules
are repositories of resident Golgi apparatus proteins protected from turnover during the flow differentiation of the flattened
saccules of the Golgi apparatus stack.
Accepted: 3 November 1997 |
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